This invention relates generally to systems for measuring the magnitudes of reactions occurring between a predetermined class of components in a liquid specimen and their corresponding conjugates coated on a carrier, and, more particularly, to systems of this kind having means for correcting for the effects of background noise and non-specific reactions of the components to the carrier.
Systems of this general type are of particular use in immunological applications. For example, an insoluble carrier coated with a known quantity of a single antigen or antibody can be incubated with a liquid specimen to determine the presence in the specimen of a conjugate for the coating, i.e., the corresponding antibody or antigen. In some systems, a number of separate binding components, particularly antigens, are coated on spaced regions of a cellulosic carrier, for simultaneous incubation with a single liquid specimen.
After incubation, the magnitudes of any resulting reactions are measured to determine the concentration of antigen-specific antibodies in the specimen. These measurements can be made using techniques like radioimmunoassay, in which the carrier is incubated with a liquid containing radioactively-tagged antibodies that bind to any antibody previously bound to the antigen-coated carrier. The presence of any radioactivity on a particular region of the carrier can then be measured, for example, by means of a gamma counter, or, alternatively, by exposing photographic film and then measuring the optical density of a resulting photographic print. A copending and commonly-assigned application for U.S. Patent, Ser. No. 308,935, filed in the name of Vincent A. Marinkovich and entitled "Multiple-Component Binding Assay System And Method Of Making And Using It" now issued as U.S. Pat. No. 4,459,360, describes this incubation and measurement technique in greater detail.
Although the technique described above for measuring the magnitudes of reactions has proven generally effective, it is not believed to be as accurate as is possible. This is due, in large part, to the effects of background noise and non-specific reactions between components in the liquid specimen and microscopic portions of the carrier not coated with conjugates such as antigens. Such background noise and non-specific reactions have the effect of increasing the apparent magnitude of the reactions occurring on the carrier.
Some systems in the past are believed to have corrected for the occurrence of non-specific reactions by subtracting out from each measurement a fixed value that is assumed to exist. This technique is not entirely satisfactory, however, because it is believed that the amount of such non-specific reactions can vary significantly for a number of specimens.
It should therefore be appreciated that there is a need for a system that measures reactions occurring between a predetermined class of components in a liquid specimen and their corresponding conjugates coated on a carrier, and that accurately corrects for the effects of non-specific and background noise. The present invention fulfills this need.